Inhibition of radiation-induced transformation of C3H/10T½ cells by chymotrypsin inhibitor 1 from potatoes

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Abstract
In this report, we have investigated whether a protease inhibitor obtained from potatoes (chymotrypsin inhibitor 1; CI-1) will inhibit carcinogen-induced transformation of C3H/10T½ cells. CI-1 was as effective as the soybean-derived Bowman Birk inhibitor at suppressing radiation-induced transformation of C3H/10T½ cells, at a concentration of 10 μg/ml. The inhibitor was not toxic to the cells at concentrations of 0.1 –10 μg7sol;ml, the concentrations of CI-1 employed in the transformation experiments. To investigate the interaction of this inhibitor with the target cells, binding studies were carried out. 125I-labelled CI-1 could not be displaced from C3H7sol;10T½ cells by co-incubation of the cells with a 5000-fold excess of unlabelled inhibitor. These results suggest that this inhibitor does not reversibly bind to specific receptor proteins on the surface of these cells.